There is no command line scanning function with the free home version only the pro version. You may also schedule scan with the Pro version.
There is a work around for the Home version.
Check This out - HOWTO: Scheduled Automatic Scans avast! Home Version!
The major disadvantage with the task scheduler trick of using ashquick.exe is, it will scan every file of the hdd, partition, folder or file that you set it to scan; even those files not considered a potential threat, this can take a long time. It is possible to add certain folders to the exclusions list for say your media files, etc. This could leave you vulnerable if that folder got infected as it wouldn't be scanned by the on-demand scanner as you have excluded it.
The Pro version gives a lot more flexibility and the scan would follow the settings and exclusions, etc. of the regular scan.
With the different levels of protection of protection and the fall back of the Standard Shield, I find the need for daily scheduled scans lessened. I prefer to do a manual scan with my regular weekly maintenance tasks.
1. as far as I'm aware this isn't possible. First there would need to be an internet connectionopen, avast doesn't establish one, just checks if one exists. With avasts incremental autoupdate function, there shouldn't really need to schedule an update.
2. the boot-time scan requires interaction between avast and the windows environment boot function after you have selected you want to schedule boot-time scan (a number of files need to be changed to schedule a boot-time scan), so I don't see how this could be achieved with a simple comand line batch file.
The main reason a boot-time scan is required it deal with files that are either in use or in system folders and as such protected by windows. So again I'm unsure why this would be required on a regular (schedule) basis.